Aromatic hydrocarbons and their halogen derivatives as antifoggants



Patented Apr. 8, 1947 AROMATIC HYDROCARBONS AND THEIR HALOGENDERIVATIVES AS ANTIFOG- GANTS George E. Fallesen, Rochester, N. Y.,assignor to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey No Drawing. Application January 13, 1944, Serial No. 518,120

19 Claims.

This invention relates to fog inhibitors for photographic emulsions andto photographic emulsions containing them.

It is known that photographic emulsions, particularly ultra-sensitiveemulsions, exhibit a tendency to form a deposit of silver in theunexposed emulsion. This deposit extends more or less uniformly over theentire emulsion and is known as fog. Photographic fog is of two types,local and general. Local fog is formed by exposure of the film or plateat undesired points, as by a light leak in the camera, or by localaction of chemicals. General fog or, as it is sometimes known, chemicalfog, is formed in a number of ways. It may be caused by the conditionsunder which the film or plate is stored, such as conditions of hightemperature or unusually long time of storage. The nature of theemulsion may also produce chemical fog, as well as conditiom ofdevelopment of the emulsion, as by development for protracted periods oftime or at temperatures above normal. Highly sensitive emulsions aremore likely to fog than those of lower sensitivity. I am concernedprimarily with general or chemical fog.

It is an object of the present invention to provide antiiogging or foginhibiting agents for ultra-sensitive photographic emulsions and therebyto preserve the emulsions against deterioration resulting in fog. Afurther object is to provide antifogging agents which do not markedlylower the sensitivity of the emulsion. Other objects will appear fromthe following description of my invention.

These objects are accomplished by developing an exposed silver halideemulsion in the presence of an aromatic hydrocarbon or a halogenatedaromatic hydrocarbon. I prefer to use aromatic hydrocarbons of thebenzene series having a phenyl substituent or a halogen substituent or alower alkyl substituent such as a methyl or ethyl substituent.

These compounds may be incorporated in an emulsion to which may be addedoptical sensitizing dyes. The emulsion may be one which is intended tobe used directly after emulsification or one which is subjected toripening. In some cases the fog inhibiting efiect of the hydrocarbons orhalogenated hydrocarbons is evident only in unsensitized emulsions or inemulsions which have been stored or incubated for an appreciable periodof time.

Hydrocarbons and halogenated hydrocarbons which I have found suitablefor use according to my invention, comprise the following examples:

CH: CzHs CH /CH3 s CH; CHa Cumene p-Cymene Diethylbenzcne Diphenyl CH H.Durcns Ethylbenzene Fluorene CH: 02H; CH;

CH --CH: ozHs 0:115

CH CH; CzH5 CzHs CH CH3 CH3 CzHs Hexon ethylbenzene HexacthylbenzeneMesltylcne (EH: (I'JHm cm- CH1 0H8 Ha a Naphthalene PentamethylbenzenePseudocumene CH3 CqHg CH3 B1 40 C2H5 C2115 O-CH; Q TolueneTrlethylbenzene Xylene Bromobenzeno CH: CH: OH=CH1 -Br -Br /CH: CHa- CH35 CH2! 2-bromocymene Bromomesitylene Bromostyrene The antifoggantproperties of the compounds used according to my invention were testedas follows: I

Silveniodobromide was precipitated in 0.8% gelatin solution. Afterprecipitation was complete this entirevolume of emulsion was cooled anddivided intoa portions weighing 1643 grams each. To each portion wasadded enough gelatin to increase the gelatin concentration toapproximately6.6%. Each portion was then heated to the requireddigestion temperature, that is, about 60*--'C. and assoon as this"temperature was reached a certain amount of the compound to be tested,e. g., 25., rams of cumene, dissolved in 300 cc. of inethylalcohol, wasadded. Digestion was then continued for 30 minutes at the specifiedtemperature and the emulsion was then. chilled cal conditions for 14days.

4 hating from the same halide.

After washing, each emulsion was heated to the optimum point for maximumspeed and precipitation of silver gamma with acceptable fog;Unsensitized and panchromatized samples of each emulsion so finishedwere coated by machine on glass plates.

After the plates were dry, a series of sensitometric tests were made onthem. The data were then comparedwiththose of the check emulsioncontaining no addendum. These tests include initial tests for speed,gamma and fog, made on the day after coating, similar tests on a secondset of plates incubated at 120 F., dry heat, for

"6days and'.a thirdset of tests made on a third set of plates afterhaving been kept under tropi- (The tropical conditions are simulated byvarying the temperatureand humidity through a cycle to reproduce day andnight conditions in tropical climates.) Plates for each of-these testsWere developed 'for 3 minutes at F. in; Kodak D-IQ developer which hadthe following composition:

Monomethyl-p-aminophenol sulfate grams 2;2 Sodium sulfite (desiccated)do. 96 Hydroqu'inone do .L83 Sodium carbonate (desiccated) do 48Potassium bromide do 5 Water to"-.. lliters -1 The Iresults "of thesetests are 'tabulatedfbelow, in each case the amountfof fhydrocarbonlorhalo g-enated hydrocarbon being 12.5 "gramsper. 1000 cc. of.unsensitize'dWet'emulsion.

Hydrocarbons TropicalCondition :14- V w v 4 V 6-Day 1203 F. DRY. Tn Inital Fog Tests gasylncubanon Fog hcubaflonlaog, Tests Name of CompoundEmulsion Emulsion Emulsion: Emulsion. Emulsion. Emulsion with Comwithoutwith Comwithout I with Comwithout pound Compound pound Compound poundCompound Curnene Q05 10 Diethyl benzene. (I5. J. 10 Mesitylene -10Pcntarnethylbenzcnen 10 Pscudocumcne .09 Toluene .ElO 'Tricthylbenzenc10 o-Xylcne .10 p-Xylene .10

Halogenated hydrocarbons Tropical Conditionlfi i s; 6-Day-120 -F,-Dryln-Initial FogTcsts lgggthsicuba bubafion-Fqgvregts Name of Compound 7Emulsion Emulsion :Emulsion Emulsiorn Emulsion Emulsion; with Com-"without with Comwithout with Com; without pound CompoLmd pound'lGompound pound Compound.

Bromobenzcne 07 05 O9 12 09;: 17 2-Bromocymene... .04 05 .05, 17 04 12Bromomesitylene. :03 .05 {04" 17 :05 12 Broniostyre'ne .031 .05.v .06..17. 1.05;: M12 o-Bromotolue nm. 09 1 -09. .-09 a. .316 24 1,2,4,fi'letrabrorno'bcnzene .07' 09 :06" 141 ."08 B-Phen ylethylbromidm U4 05'.3:04, .17 .114 v. -I2. .Iodobenzenc .05 .05 .20 v 1 2+ Fluorobcnzene .0506 (19' 13 o'Tluorochlorobenzene .041. 05 .05 1'4 a 1 8 weeks undertropical conditio and stored in preparation for shredding and washing.One of these portions received no additions other than the requiredgelatin and it served as' the controlior all the portions origi- Theamount of fog was determined-by;r-eading the. density :on theunexposedarea -of--the.vtest atter exposure and development of the emuisionp mt us-ual-manner. Y

- hydrocarbons were introduced into the emulsion immediately afterprecipitation of the silver halide and after the emulsion had beenraised to, the digestion temperature but before digestion was complete.I have also found that bromohydrocarbons may be added to the emulsionsafter washing and before finishing and that, when added at this stage,they stabilize the sensitivity of panchromatic emulsions. Thisstabilization of panchromatic sensitivity is in addition to theantifoggant properties which the compounds possess. Ordinarily theemulsion, after digestion, is chilled, shredded and washed and, whenready for coating, is heated to the optimum point for maximum speed andgamma with acceptable fog. The emulsion is then coated or dried. If thebromohydrocarbon is added to the emulsion just prior to this heating towhich the emulsion sensitivity of the emulsion is retained for a greaterperiod of time upon storage of the emulsion. The effect of thebromohydrocarbons in stabilizing the red sensitivity of an emulsion wastested 'by preparing a panchromatic emulsion in the usual way asdescribed above but without addition of an antifoggant. Bromomesitylenewas then added in varying amounts to portions of the emulsion just priorto finishing, that is, prior to the heating step to which the emulsionwassubjected before coating and plates were coated from these variousportions of the emulsion. The plates were then kept for 8 weeks undertropical conditions and were then exposed on a sensitometer anddeveloped in Kodak D-19 developer. The check emulsion to which nobromohydrocarbon had been added lost 45% of its speed whereas the lossin emulsions to which bromomesi'tylene had been added ranged from 12 to22%. The fog was also lower in the emulsions to which thebromomesitylene had been added than in the check emulsion.

The following table shows the results obtained upon addingbromomesitylene to the emulsion in this way, the percentage of originalspeed of the emulsions and the fog in the various coatings beingrecorded in the table.

The fog inhibiting agents which I have described may be used in variouskinds of photographic emulsions. In addition to being useful in ordinarynon-sensitized emulsions, some of them may be used in orthochromatic,panchromatic and X-ray emulsions. Various silver salts may be used asthe sensitive salt such as silver bromide, silver chloride, silverbromoiodide, and silver chlorobromide. The dispersing agent may begelatin or other suitable colloid, such as collodion, albumen, celluloseorganic derivatives or synthetic resins.

It is known that synthetic waxes, such as chlorinated naphthalenesandchlorinated diphenyls have been used as lubricants in photographicemulsions. I do not use such materials, but employ halogenatedhydrocarbons which are nonwaXy, monomeric compounds of relatively lowmolecular weight. The chlorinated hydrocarbon waxes which havepreviously been used to lubricate film are believed to be polymericsubstances.

is subjected before coating, the panchromatic hydrocarbon of thebenzeneseries having a substituent selected from the classconsisting ofhalogen atoms,an unsubstituted phenyl radical, unsubstituted loweralkylradicals, and halogen substituted lower alkyl radicals, said hydrocarbonbeing free from other substituent groups.

2. A gelatino-silver halide emulsion containing from 1-15 grams perliter of Wet emulsionof a non-Waxy aromatic hydrocarbon of the benzeneseries having a substituent selected from the class consisting ofhalogen atoms, an unsubstituted phenyl radical, unsubstituted loweralkyl radicals and halogen-substitutedlower alkyl radicals, saidhydrocarbon being free from other substituent groups.

3. The method of reducing the amount of fog produced upon development ofa silver halide emulsion which comprises developing said emulsion in thepresence of a fog-inhibiting amount of a non-waxy aromatic hydrocarbonof the benzene series having a substituent selected from the classconsisting of halogen atoms, an unsubstituted phenyl radical,unsubstituted lower alkyl radicals, and halogen-substituted lower alkylradicals, said hydrocarbon being free from other substituent groups.

4. A gelatino-silver halide emulsion containing a fog-inhibiting amountof a non-waxy halogensubstituted aromatic hydrocarbon of the benzeneseries free from other substituent groups.

5. A gelatino-silver halide emulsion containing a fog-inhibiting amountof a bromobenzene.

6. A gelatino-silver halide emulsion containing a fog-inhibiting amountof a fiuorobenzene.

'7. A gelatino-silver halide emulsion containing a fog-inhibiting amountof a non-waxy aromatic hydrocarbon of the benzene series having an alkylsubstituent group selected from the class consisting of methyl and ethylgroups, and free from other substituent groups.

8. A gelatino-silver halide emulsion containing a fog-inhibiting amountof a methylbenzene.

9. A gelatino-silver halide emulsion containing from 1 to 15 grams perliter of Wet emulsion of a non-waxy halogen-substituted aromatichydrocarbon of' the benzene series free from other substituent groups.

10. A gelatino-silver halide emulsion containing from 1 to 15 grams perliter of Wet emulsion of a bromobenzene.

11. A gelatino-silver halide emulsion contain ing from 1 to 15 grams perliter of wet emulsion of a fiuorobenzene.

12. A gelatino-silver halide emulsion containing from 1 to 15 grams perliter of wet emulsion of a non-waxy aromatic hydrocarbon of the benzeneseries having an alkyl substituent group selected from the classconsisting of methyl and

